1. Field of the Invention
This invention relates to a rear blade mounting apparatus for a bulldozer. In particular, the invention relates to a blade apparatus and its control method, which blade is mounted to the rear of the bulldozer such that the rear blade can be operated in lift or tilt modes.
2. Brief Description of Prior Art
In the construction industry, labor and capital equipment costs are primary variables that effect the cost of a particular project. Large machinery is used to more efficiently handle tasks that were originally accomplished by hand, such as digging, lifting, and moving objects. For example, bulldozers are commonly used on construction job sites for digging, pushing and removing large amounts of earth for mining, grading and other tasks. 
A bulldozer is typically a tractor-like machine having a forwardly mounted bucket that extends forward of the body of the bulldozer. The bulldozer further includes a pair of extending loader arms pivotally connected to the tractor, and said bucket pivotally mounted on free ends of the loader arms. Hydraulic cylinders, or the like, are mounted on the loader arms and controlled to cause the bucket to be positioned in various desired positions. The bucket can be lifted over the body or placed on the ground. Further, the orientation of the bucket can be controlled to hold dirt or the like or to dump the same.
The rear of the tractor may include an attachment that trails the body of the bulldozer such as a ripper, or a winch, or the rear of the tractor may not include any such accessory.
While these tractors in general, are effective in collecting and removing earth, especially large chunks of earth, these tractors have some limitations. In particular, a conventional bulldozer having said forwardly mounted bucket when collecting and removing earth from a mine pit for example, cannot pivot so that the bucket will collect the fine material remaining at or near the walls of such pit. Depending upon the size of the pit, there are often large volumes of such materials remaining. Often such remaining material must be shoveled by hand into a dump truck for transporting away. Such manual procedure requires additional manpower which is not only dangerous due to such manpower working near large machinery, but also costly, time consuming, and generally inefficient. The inventor herein is unaware of any attachment to the bulldozer available for collecting such materials at or near the walls of the mine pit work site. 
As will be seen from the subsequent description, the preferred embodiments of the present invention overcome these and other shortcomings of prior art.